This invention relates to an inhalation apparatus for dispensing substances for inhalation and, in particular, but not exclusively, for dispensing medicinal products in aerosol form from a pressurised dispensing container.
It is well-known when dispensing medicinal products orally, for instance in the treatment of asthma, that the effectiveness of treatment depends to a large extent on the successful delivery of the medicament to the lower part of the lungs of the user. It has been found that the successful delivery of medicament to the lungs of the user is affected by the timing of the delivery in relation to the inhalation cycle of the user. Attempts have been made to coordinate the delivery of medicament with the inhalation cycle of the user and to use the inhalation of the user as the trigger for actuation of the pressurised dispensing container.
However, a disadvantage with a number of these attempts is that the resulting apparatus is difficult to use, requiring skill and training of the user. Thus, these devices are unsuitable for use with small children or the infirm who have difficulty in correctly operating the devices. Another disadvantage has been the inconsistency in performance of the devices. Variations in ambient temperature and pressure tend to alter the material and mechanical properties of components of the devices. This is especially the case for sealing members manufactured from elastomers or rubbers which tend to xe2x80x9cstickxe2x80x9d when the ambient temperature is raised. This sticking leads to inconsistent movement of the component and to a user of the device having to impart a greater force when inhaling to operate the device.
An object of the present invention is to provide an inhalation apparatus in which mechanical means are used to co-ordinate the delivery of product with the inhalation cycle of the user. It is a further object of the present invention to provide an inhalation apparatus in which the actuation of the apparatus is consistently triggered by the inhalation of the user.
The present invention provides inhalation apparatus for dispensing a product comprising a housing adapted to receive a pressurised dispensing container and a mouthpiece, a duct for conveying, in use, product from the container to the mouthpiece, a sliding seal member movable under action of triggering means between a first position in which the duct is closed and a second position in which the duct is open, wherein a spring means is provided to bias the sliding seal member towards the second position, at least one air inlet for allowing air into the housing and a flow sensor being activatable, by means of an airflow created when a user applies suction to the mouthpiece, to activate said triggering means such that said sealing member is moved by said spring means into its second position to allow product to be dispensed into the airflow.
In a first embodiment, the flow sensor comprises an air inlet valve means biased to seal said at least one air inlet comprising a vane, the vane being movable from a first position, in which the vane seals the at least one air inlet and the sealing member is held in the first position, to a second position in which the vane unseals the at least one air inlet and the sealing member is moved into the second position.
In a second embodiment the flow sensor comprises a diaphragm and a vane, the diaphragm being movable in response to the airflow to contact and move the vane from a first position, in which the sealing member is held in the first position, to a second position in which the sealing member is moved into the second position.
The diaphragm comprises a first rigid element connected to the housing and a second rigid element slidably movable relative thereto, the first and second diaphragm elements being connected by a flexible member.
The triggering means preferably comprise a cantilever being rotatably fixed at one end to the housing and being rotatable from a first position, in which another end of the cantilever is supported by the vane such that the cantilever is in contact with and maintains the sealing member in its first position, to a second position, in which the free end is unsupported by the vane and the cantilever moves out of contact with the sealing member such that the sealing member is able to move to its second position.
Preferably the triggering means further comprises a cam member having a cam surface at least a portion of which is contactable with the cantilever, wherein movement of the cam member moves the cantilever from its second position to its first position.
Alternatively, the triggering means comprises a leaf spring rotatably fixed at one end to the housing and rotatably fixed at the other end to the vane and movable from a first position in which the leaf spring is in contact with and maintains the sealing member in its first position, to a second position, in which the leaf spring moves out of contact with the sealing member such that the sealing member is able to move to its second position.
Preferably the triggering means further comprises a cam member having a cam surface at least a portion of which is contactable with the leaf spring, wherein movement of the cam member moves the leaf spring from its second position to its first position.
As a further alternative, the triggering means comprise a linkage means comprising first and second struts rotatably connected to one another, a distal end of one strut being rotatably fixed to the housing and a distal end of the other strut being rotatably fixed to the vane, the linkage means being movable from a first position in which the linkage means is in contact with and maintains the sealing member in its first position, to a second position, in which the linkage means moves out of contact with the sealing member such that the sealing member is able to move to its second position.
Preferably the triggering means further comprises a cam member having a cam surface at least a portion of which is contactable with the linkage means, wherein movement of the cam member moves the linkage means from its second position to its first position.
Preferably the present invention further comprises a mouthpiece cover moveable from a first position in which the mouthpiece is sealed to a second position in which the mouthpiece is unsealed.
Preferably the cam member is located on the mouthpiece cover, wherein movement of the mouthpiece effects movement of the cam surface relative to the cantilever.
Preferably the present invention further comprises support means for supporting, in use, a pressurised dispensing container and a rod extending between the support and the mouthpiece cover to maintain a fixed distance therebetween when the mouthpiece cover is in its first position, wherein movement of the mouthpiece cover from its first to second position causes the pressurised dispensing container to become unsupported by said rod and allows it to move under bias of a spring to effect depression of a valve stem of the dispensing container.
Preferably the duct means comprises a dispensing channel and a bore extending laterally therefrom and the sealing member is slidable within the dispensing channel, the sealing member comprising a sealing element sealing radially against an inner surface of the dispensing channel, wherein when the sealing member is in its first position, the seal between the sealing element and the dispensing channel is at a position which prevents product from reaching the lateral bore, and when the sealing member is in its second position, the seal is at a position such that product is able to be discharged through the lateral bore into the mouthpiece.
Preferably the sealing element is frusto-conical.
Preferably the sealing element is an elastomer or rubber.